Experimental and numerical study on heat transfer characteristics of tangential effusion cooling for a combustor liner

A great number of studies have been conducted on effusion cooling, which is based on the flat plate. However, the differences in flow and heat transfer characteristics between a flat plate and a circular combustor restricted the immediate application of the previous studies to the design of combustor cooling. In this study, a new type of effusion cooling with tangential injection based on the cylinder, which was fabricated by electric discharging machining, is employed in the present investigation using infrared imaging technique. With the blowing ratio ranging from 2.2 to 17.9, the results of proposed structure were compared with that of effusion holes based on the flat plate. The compound angles (β) of tangential effusion are 45°, 60°,75°, 95° respectively. Results show that compared to the effusion cooling based on the flat plate, the cooling jets of the tangential effusion based on the cylinder have a large tangential velocity component, which keeps the cooling jets attached to the wall and flowing spiral forward. The overall cooling effectiveness of tangential effusion is about 50% higher than effusion holes based on the flat plate. This also indicates that the existing conclusions of effusion cooling based on the flat plate cannot be directly applied to the combustion chamber. The cooling performance of tangential effusion cooling is greatly influenced by the compound angle and the 75° is optimal among them. In the studied range of blowing ratio, the overall cooling effectiveness of tangential effusion is above 0.8, and there is a significant cooling enhanced with the increase of blowing ratio. This provides a reference and database for the cooling design for low-emission combustion chambers with low cooling consumption.